Calvert Cliffs nuclear unit restarts

Calvert Cliffs nuclear power plant in southern Maryland restarted one of its two reactors Thursday after fixing the mechanical problem that caused its shutdown two days earlier, a Constellation spokesman said.

Unit 2 reconnected to the regional electric grid at 8:50 a.m. after workers fixed a faulty coupling on a pump feeding water into one of two steam generators at the plant, said Kory Raftery, spokesman for Constellation Energy Nuclear Group.

Operators shut the reactor down Tuesday morning after vibrations caused the pump to stop operating, Raftery said. The vibrations were traced to the failure of the coupling, which connects the pump with its motor. Unit 1 continued to operate at 100 percent power.

The two-day outage was the second for Unit 2 in two weeks. The reactor "scrammed" unexpectedly May 8 after an electrical malfunction caused some valves to close that feed steam to the turbine. The reactor shut down automatically then to stop the buildup of pressure in its cooling system. It was out of service for five days while plant workers repaired and tested the valves.

The two shutdowns were unrelated, said spokesmen for both Constellation and the Nuclear Regulator Commission. The NRC's Neil Sheehan said the safety agency monitors such events and would increase its oversight of a nuclear plant if it has more than three unplanned shutdowns in roughly 10 months' operation.

Vice President Joe Biden's associates have resumed discussions about a 2016 presidential run after largely shelving such deliberations while his son was sick and dying earlier this year. But Biden has yet to tell his staff whether he will run or personally ask them to do any planning for a potential...